Electric toothbrush

ABSTRACT

On a tip of a main body case is formed a cylindrical brush attachment shaft tube to which a toothbrush head (holding unit) is removably attached. In a space within the cylindrical brush attachment shaft tube is disposed a motor to which an eccentric weight generating vibration is attached. Therefore, it is possible for the tip of the toothbrush head to approach the main body case side by the length of the cylindrical brush attachment shaft tube, thereby shortening the total length of an electric toothbrush.

TECHNICAL FIELD

The present invention relates to an electric toothbrush.

BACKGROUND ART

In the prior art, various types of electric toothbrushes (e.g., patentdocument 1) have been proposed in which the toothbrush rotates aneccentric weight with a motor to generate oscillation and transmit theoscillation to the toothbrush bristles so as to improve the plaqueremoval performance (teeth brushing performance).

Over these recent years, people have become conscious of oral hygieneand thus have started to brush their teeth when at work or whiletraveling. As a result, electric toothbrushes having superior brushingfunctions are more frequently used when people brush their teeth atwork, while traveling, or the like.

PRIOR ART LITERATURE Patent Document

Patent Document 1: Japanese Laid-Open Patent Publication No. 9-168554

SUMMARY OF THE INVENTION Problems that are to be Solved by the Invention

An electric toothbrush requires an oscillation generator, which isformed by a motor including an eccentric weight, a battery, which drivesthe oscillation generator, and the like. This enlarges the toothbrushmaking the toothbrush bulky and inconvenient when carried in a bag, apouch, or a pocket.

Thus, there is a demand for a toothbrush that is compact and hassuperior portability but does not lower the teeth brushing performance.

The present invention solves the above problem. The object of thepresent invention is to provide an electric toothbrush that is compactand has superior portability and superior teeth brushing performance.

Means for Solving the Problem

The means for achieving the above object will now be described.

An electric toothbrush of the present invention is provided with atoothbrush head, an oscillation generator formed by a motor including aneccentric weight, and a main body case attached in a removable manner tothe toothbrush head and accommodating the oscillation generator. Thetoothbrush head is attached to a brush attachment shaft tube at a distalend of the main body case, and the oscillation generator is arranged inthe brush attachment shaft tube.

In the electric toothbrush, preferably, the brush attachment shaft tubeis arranged biased toward a rear surface side of the main body case.

The electric toothbrush, preferably, further includes a cap fitted ontothe main body case to accommodate the toothbrush head that is attachedto the brush attachment shaft tube.

In the electric toothbrush, preferably, the main body case includes anouter case, which includes the brush attachment shaft tube, and an innercase, which includes a motor accommodation portion that accommodates themotor at one end and a battery accommodation portion that accommodates abattery for driving the motor at another end. The inner case isaccommodated in the outer case so that the motor accommodation portionis press-fitted into the brush attachment shaft tube of the outer case.

The electric toothbrush, preferably, further includes a seal ringarranged between the outer case and the inner case of the main bodycase.

In the electric toothbrush, preferably, the brush attachment shaft tubeis entirely arranged in the toothbrush head when the toothbrush head isattached to the main body case.

Effect of the Invention

The present invention provides an electric toothbrush that is compactand has superior portability and superior teeth brushing performance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of an electric toothbrush in a first embodiment;

FIG. 2 is a side view showing the electric toothbrush from which atoothbrush head is removed;

FIG. 3 is a side view showing the electric toothbrush to which a cap isattached;

FIG. 4 is a front view showing the electric toothbrush to which the capis attached;

FIG. 5 is a cross-sectional side view showing the electric toothbrush;

FIG. 6 is an enlarged cross-sectional side view showing part of theelectric toothbrush;

FIG. 7 is an enlarged cross-sectional side view showing part of theelectric toothbrush; and

FIG. 8 is a cross-sectional side view showing an electric toothbrush ina further example.

EMBODIMENTS OF THE INVENTION

A first embodiment of the present invention will now be described withreference to the drawings.

In the drawings, arrows L1, L2, T1, and T2 respectively indicate adistal direction L1, a basal direction L2, a frontward direction T1, anda rearward direction T2.

Referring to FIG. 1, an electric toothbrush 1 includes a main body case2, a grip case 4, which is fitted to a basal side of the main body case2, a toothbrush head 5, which is fitted to a distal side of the mainbody case 2, and a cap 6, which is fitted to the main body case 2attached with the toothbrush head 5 as shown in FIG. 3.

Referring to FIGS. 5 and 6, the main body case 2 includes an outer case10 and an inner case 20. The outer case 10 accommodates the inner case20, and the inner case 20 accommodates electric components that applyoscillation to the toothbrush head 5.

With reference to FIGS. 5 and 6, the terms related to the electrictoothbrush 1 will now be defined:

(A) A cross-sectional plane that includes a rotation shaft MC of a motorM and brush bristles 52 of the toothbrush head 5 and is parallel to therotation shaft MC of the motor M defines a cross-sectional side plane;

(B) In the cross-sectional side plane, the side of a center axis C3 ofthe grip case 4 including a distal end portion of the brush bristles 52of the toothbrush head 5 is defined as a front side. In thecross-sectional side plane, the side of the center axis C3 of the gripcase 4 opposite to the front side defines a rear side;

(C) In a direction extending along the center axis C3 of the grip case4, a portion of the outer case 10 located between the toothbrush head 5and the grip case 4 is defined as a case intermediate portion 16.Further, in the cross-sectional side plane, walls at the front side ofthe outer case 10, the inner case 20, and the toothbrush head 5 arerespectively defined as front walls 10 d, 20 d, and 5 d. In thecross-sectional side plane, walls at the rear side of the outer case 10,the inner case 20, and the toothbrush head 5 are respectively defined asrear walls 10 c, 20 c, and 5 c;

(D) In the cross-sectional side plane, an outer surface of the frontwall 5 d in the toothbrush head 5 is defined as a front surface 51 b.Further, an outer surface of the rear wall 5 c in the toothbrush head 5is defined as a rear surface 51 a; and

(E) Among the end portions of the toothbrush head 5, the side of thebrush bristles 52 is defined as a distal end portion. Further, among theend portions of the toothbrush head 5, the end portion opposite to thedistal end portion is defined as a basal end portion.

As shown in FIGS. 5 and 6, the outer case 10 is a case having the formof a bottomed tetragonal tube that is chamfered and formed from ABSresin. Part of the distal side of the outer case 10 is narrowed to forma brush attachment shaft tube 11. The brush attachment shaft tube 11,which has the form of a bottomed tetragonal tube, includes a distal endportion closed by a top wall 11 a. The brush attachment shaft tube 11 ishollow and defines, for example, a tubular void S1 (refer to FIG. 6).The void S1 is in communication with a void S2 (refer to FIG. 6), whichhas the form of a tetragonal tube, in the outer case 10. As shown inFIG. 2, the center axis C1 of the brush attachment shaft tube 11 isbiased toward the rear surface 10 a of the outer case from the centeraxis C2 of the outer case 10.

The brush attachment shaft tube 11 is fitted into the toothbrush head 5from an open basal end of the toothbrush head 5. In the caseintermediate portion 16, the end portion at the side of the toothbrushhead 5 is arranged continuously with the brush attachment shaft tube 11.The front wall 10 d of the case intermediate portion 16 is arranged infront of the front wall 10 d of the brush attachment shaft tube 11. Thisforms a step at the boundary between the case intermediate portion 16and the brush attachment shaft tube 11. The toothbrush head 5 isattached to the main body case 2 so that an end face 53 of the basal endportion of the toothbrush head 5 faces toward an end face of the step.

In the cross-sectional side plane, the front wall 20 d of the inner case20 is arranged at the front side of the motor M. The front wall 10 d ofthe outer case 10 is arranged at the front side of the front wall 20 dof the inner case 20. The front wall 5 d of the toothbrush head 5 isarranged at the front side of the front wall 10 d.

A through hole 12 extends through the front surface 10 b of the outercase 10. The through hole 12 is closed by an elastic switch member 13.The switch member 13 is formed by an elastomer resin and welded to therim of the through hole 12. A user can push the switch member 13 intothe void S2.

The voids S1 and S2 of the outer case 10 accommodate the inner case 20.The inner case 20 includes a trunk 21, which has the form of a chamferedtetragonal tube at a generally central position. The trunk 21 has aprofile having the same shape as the inner circumferential surface ofthe outer case 10. About one half of the trunk 21 at the distal side isarranged in the void S2 of the outer case 10.

The trunk 21 includes a basal end portion defining a batteryaccommodation portion 22 formed by cutting out one half of a bottomedtubular body and opening the rear side. When about one half of the trunk21 at the distal side is arranged in the void S2 of the outer case 10,the battery accommodation portion 22 is not accommodated in the outercase 10 and is exposed in the basal direction L2 from the outer case 10.A positive electrode terminal fitting 23 and a negative electrodeterminal spring 24, which extends from the trunk 21, are arranged in thebattery accommodation portion 22. A battery B, for example an AAAbattery, is accommodated and held in the battery accommodation portion22 in a state electrically connected to the positive electrode terminalfitting 23 and the negative electrode terminal spring 24.

The distal side of the trunk 21 defines a substrate fastening portion25. The substrate fastening portion 25 is arranged at a location whereit faces the switch member 13, which is arranged in the outer case 10,when about half of the trunk 21 at the distal side is arranged in thevoid S2 of the outer case 10. A printed wiring substrate 26 is fixed tothe substrate fastening portion 25. A switch SW, which is electricallyconnected to the positive electrode terminal fitting 23 and the negativeelectrode terminal spring 24, is mounted on the printed wiring substrate26. The printed wiring substrate 26 is positioned to face the switchmember 13, which is arranged in the outer case 10. Accordingly, when theswitch member 13 is pushed with a finger, the switch SW is turned on andoff by the pushed switch member 13.

The distal side of the substrate fastening portion 25 includes a motoraccommodation portion 27, which is formed by cutting out one half of abottomed tubular body and opening the rear side. When the trunk 21 isarranged in the void S2 of the outer case 10 of the trunk 21, the motoraccommodation portion 27 is arranged in the void S1 of the brushattachment shaft tube 11. When the motor accommodation portion 27 isarranged in the void S1 of the brush attachment shaft tube 11, the outercircumferential surface of the motor accommodation portion 27 comes intoclose contact with the inner circumferential surface of the brushattachment shaft tube 11.

As shown in FIGS. 5 and 6, the motor accommodation portion 27accommodates a motor M. When the motor accommodation portion 27 isarranged in the void S1 of the brush attachment shaft tube 11, the outercircumferential surface of the motor M, which is exposed from the motoraccommodation portion 27, comes into contact with the innercircumferential surface of the brush attachment shaft tube 11 through aspacer 28, which serves as a transmission member. The rotation shaft MCof the motor M is arranged toward the rear from the center axis C2 ofthe grip case 4. Further, the rotation shaft MC projects into the voidS1 from the distal surface of the motor accommodation portion 27. Aneccentric weight 29 is fixed to a projecting portion of the rotationshaft MC.

The front outer surface of the motor M directly contacts the front wall20 d of the inner case 20.

As shown in FIGS. 5 and 6, the spacer 28 is arranged between the rearouter surface of the motor M and the rear wall 20 c of the inner case20. The spacer 28 directly contacts both of the rear wall 10 c of theouter case 10 and the motor M.

In the cross-sectional side plane, the front wall 20 d of the inner case20 is arranged at the front side of the motor M. The front wall 10 d ofthe outer case 10 is arranged at the front side of the front wall 20 dof the inner case 20. The front wall 5 d of the toothbrush head 5 isarranged at the front side of the front wall 10 d of the outer case 10.The spacer 28 is arranged at the rear side of the motor M. The rear wall10 c of the outer case 10 is arranged at the rear side of the spacer 28.The rear wall 5 c of the toothbrush head 5 is arranged at the rear sideof the outer case 10.

The switch SW is arranged on the front wall 20 d of the inner case 20.In the inner case 20, the switch SW is arranged, relative to the centeraxis C3 of the grip case 4, at a portion located on the opposite side ofthe portion where the spacer 28 is arranged.

When the switch SW mounted on the printed wiring substrate 26 is turnedon, the motor M receives voltage from the battery B and producesrotation. When the motor M produces rotation, the eccentric weight 29,which is fixed to the rotation shaft MC, rotates eccentrically about therotation shaft MC. The eccentric rotation swings the rotation shaft MCand oscillates the motor M, which is accommodated and held in the motoraccommodation portion 27. The oscillation of the motor M is transmittedthrough the motor accommodation portion 27 to the brush attachment shafttube 11, which is in close contact with the motor accommodation portion27.

One half of the outer circumferential surface of the trunk 21 of theinner case 20 at the distal side, which is arranged in the outer case10, has a smaller diameter than the other half at the basal side, whichis not arranged in the outer case 10. Thus, when the motor accommodationportion 27 of the inner case 20 is arranged in the void S1 in the distalhalf of the outer case 10 and the substrate fastening portion 25 of theinner case 20 is arranged in the void S2, the outer circumferentialsurface of the basal half of the trunk 21 engages the innercircumferential surface of the outer case 10. This restricts furthermovement of the inner case 20. Thus, the inner case 20 is arranged sothat the distal half of the trunk 21 is arranged in the outer case 10,and the basal half of the trunk 21 and the battery accommodation portion22 is exposed from the outer case 10.

A distal annular groove 30 is formed in the outer circumferentialsurface of the distal half of the trunk 21. A seal ring R1, which servesas a second elastic member, is fitted in the distal annular groove 30.The seal ring R1, which is formed by a rubber O-ring, includes an outerportion that projects from the outer circumferential surface of thetrunk 21 in a state fitted to the distal annular groove 30. Accordingly,when the inner case 20 (trunk 21) is arranged in the outer case 10, theseal ring R1 of the distal annular groove 30 is elastically deformed bythe inner circumferential surface of the outer case 10 so that the spacebetween the inner case 20 (trunk 21) and the outer case 10 is watertightand elastically supported.

As shown in FIGS. 5 and 6, an open end face 15, which serves as an endface of the basal end portion of the outer case 10, and an open end face41 of the distal end portion of the grip case 4, face each other. Abasal annular groove 31 is formed in the circumferential surface of thebasal half of the trunk 21, and an elastic ring R2, which serves as anelastic member, is fitted in the basal annular groove 31. The elasticring R2 is a ring made of an elastic synthetic resin. The presentembodiment employs a rubber O-ring used as a seal member. The elasticring R2 includes an outer portion that projects from the outercircumferential surface of the trunk 21 in a state fitted to the basalannular groove 31.

The main body case 2, which is formed in this manner, is attached to thegrip case 4 at the basal side and attached to the toothbrush head 5 atthe distal side.

The grip case 4 is a case having the form of a chamfered bottomedtetragonal tube that is formed from ABS resin. The battery accommodationportion 22 of the inner case 20 in the main body case 2 is arrangedinside the grip case 4 from a distal opening. The shape of the innercircumferential surface of the distal opening of the grip case 4conforms to the shape of the outer circumferential surface of the basalhalf of the trunk 21 so that the basal half of the trunk 21 can bearranged in the grip case.

Here, the outer case 10 is not arranged in the grip case 4, and the openend face 15 of the outer case 10 contacts the open end face 41 of thegrip case 4. The grip case 4 has a larger outer diameter than the outercase 10. Accordingly, when joining the open end face 15 of the outercase 10 and the open end face 41 of the grip case 4, the outercircumferential surface of the grip case 4 projects outward from theouter circumferential surface of the outer case 10. The open end face 41of the grip case 4 exposed to the outer side defines a step surface 41a.

As shown in FIGS. 5 and 6, the elastic ring R2 is arranged between theinner circumferential surface of the distal end portion of the grip case4 and the outer surface of the inner case 20. When the inner case 20(trunk 21) is arranged in the grip case 4, the elastic ring R2 of thebasal annular groove 31 is elastically deformed at the inner surface ofthe distal opening of the grip case 4 so that the space between theinner case 20 (trunk 21) and the grip case 4 is watertight andelastically supported. The attachment of the main body case 2 to thegrip case 4 forms a grip of the electric toothbrush 1 with the grip case4 and hermetically accommodates the battery B, which is accommodated andheld in the battery accommodation portion 22, with the grip case 4.

When a length of a portion in the front wall 20 d of the inner case 20that directly faces the grip case 4 is represented by length P and alength of a portion in the rear wall of the inner case 20 that directlyfaces the grip case 4 is represented by length Q, length Q is less thanlength P.

The toothbrush head 5, which is attached to the distal side of the mainbody case 2, includes a holding part 51. The brush bristles 52 areembedded in the distal end portion of the holding part 51. The basal endof the holding part 51 has a profile having the same shape as theprofile of the outer case 10. The basal end face 53 of the holding part51 includes a fitting hole 54. The brush attachment shaft tube 11, whichis formed on the outer case 10, is press-fitted in a removable manner tothe fitting hole 54. When the brush attachment shaft tube 11 ispress-fitted, the inner circumferential surface of the fitting hole 54comes into close contact with the outer circumferential surface of thebrush attachment shaft tube 11. Accordingly, the oscillation of themotor M, which is transmitted to the brush attachment shaft tube 11through the motor accommodation portion 27, is transmitted to the brushbristles 52 at the distal end portion through the holding part 51 of thetoothbrush head 5.

The holding part 51 is formed to narrow from the basal end toward thedistal end portion. More specifically, the holding part 51 is formed sothat the front surface 51 b approaches the rear surface 51 a, and theleft and right surfaces approach each other. That is, the distal endportion of the holding part 51 is arranged so that the distal rearsurface 51 a is located rearward from the center axis C1 of the brushattachment shaft tube 11 and frontward from the rear surface 10 a of theouter case 10 and so that the tips of the embedded brush bristles 52 donot extend outward from the front surface 10 b of the outer case 10.Further, the front surface 51 b of the holding part 51 is arrangedrearward closer to the rear surface 51 a so that the distal end portionof the holding part 51 is arranged at a rearward position. Since thefront surface of the holding part 51 does not extend outward, whenbrushing teeth, the teeth do not hit such an outwardly extending portionthat would make brushing difficult.

In the cross-sectional plane, the front walls 10 d and 20 d havethickness X1, the front wall 5 d of the toothbrush head 5 has thicknessY1, the rear walls 10 c and 20 c of the main body case 2 have thicknessX2, and the rear wall 5 c of the toothbrush head 5 has thickness Y2.

As shown in FIG. 7, in the end face 53 of the basal end of thetoothbrush head 5 and a plane parallel to and including the end face 53,a thickness obtained by adding the thickness X1 and the thickness Y1 isgreater than a thickness obtained by adding the thickness X2 and thethickness Y2.

In the toothbrush head 5, when a length of the front surface 51 b fromthe basal end portion to the distal end portion is represented by lengthV, and a length of the rear surface 51 a from the basal end portion tothe distal end portion is represented by length W, the length W of therear surface 51 a is less than the length V of the front surface 51 b.Further, the front wall 5 d of the toothbrush head 5 includes a hollowportion 55 at a location corresponding to the motor M.

The motor M, which is an oscillation source, is accommodated in thebrush attachment shaft tube 11, and the brush attachment shaft tube 11is press-fitted to the holding part 51 of the toothbrush head 5. Thus,the distal end of the holding part 51 can be arranged closer to (near)the main body case 2 for a length corresponding to the brush attachmentshaft tube 11 (overlapped amount of the brush attachment shaft tube 11and the holding part 51). As a result, the entire length of the electrictoothbrush 1 can be shortened so that the electric toothbrush 1 hassuperior portability and can easily be held in a pouch or a pocket. Itis preferable that the entire brush attachment shaft tube 11 be arrangedin the toothbrush head 5 like in the illustrated example.

As shown in FIGS. 5 and 6, the toothbrush head 5 attached to the mainbody case 2 is accommodated in the cap 6. The cap 6, which is a casehaving the form of a chamfered bottomed tetragonal tube that is formedfrom ABS resin, can be attached in a removable manner to the main bodycase 2. When the cap 6 is attached to the main body case 2, the outercircumference of the basal end portion of the toothbrush head 5 iscovered by the cap 6.

The toothbrush head 5 and the main body case 2 are fitted into the basalopening of the cap 6 and arranged in the cap 6. The innercircumferential surface in the basal opening of the cap 6 has the sameshape as the outer circumferential surface of the main body case 2. Whenthe cap 6 is attached to the main body case 2, the basal side of the cap6 comes into contact with the open end face 41 (step surface 41 a) ofthe grip case 4. This restricts further movement of the main body case2.

The cap 6 has a profile having the same shape as the profile of the gripcase 4. When the cap 6 is attached to the main body case 2, as shown inFIGS. 3 and 4, the outer circumferential surface of the cap 6 is flushwith the outer circumferential surface of the grip case 4, and theboundary of the cap 6 and the grip case 4 is unnoticeable. That is, theouter circumferential surface of the cap 6 at the side of a basal endface 61 and the outer circumferential surface at the side of the openend face 41 form a continuous surface in a state in which the cap 6 isfitted to the main body case 2. As a result, the outer circumferentialsurface of the electric toothbrush 1 is smooth. Thus, when the electrictoothbrush 1 is accommodated in a pouch or a pocket, the electrictoothbrush 1 does not get hooked to the surrounding, and the cap 6 doesnot fall off.

Further, when the cap 6 is attached to the main body case 2, the switchmember 13 arranged on the main body case 2 is arranged in the cap 6.Thus, when the electric toothbrush 1 is accommodated in a pouch or apocket, the switch member 13 is not erroneously turned on.

The advantages of the electric toothbrush 1 will now be described.

(1) In the present embodiment, the tubular brush attachment shaft tube11, which is attached in a removable manner to the toothbrush head 5(holding part 51), is arranged on the distal end of the main body case2, and the motor M, which is attached to the eccentric weight 29 andgenerates oscillation, is arranged in the brush attachment shaft tube11. Accordingly, the distal end of the toothbrush head 5 can be arrangedcloser to the main body case 2 by an amount corresponding to the lengthof the brush attachment shaft tube 11. As a result, the electrictoothbrush 1 can be shortened in length and has superior portability inwhich it can easily be put into a pouch or a pocket.

(2) In the present embodiment, the toothbrush head 5 (holding part 51)is attached to the brush attachment shaft tube 11, which is arranged inthe motor M to which the eccentric weight 29 that generates oscillationis attached. Accordingly, the brush bristles 52 embedded in the distalend portion of the toothbrush head 5 can be arranged closer to the motorM. This suppresses attenuation of the oscillation of the motor M, andthe oscillation is efficiently transmitted to the brush bristles 52.This improves the teeth brushing performance.

(3) In the present embodiment, the motor M, which generates oscillationand is arranged in the brush attachment shaft tube 11, is located at aposition that is far from the grip case 4, which is held and fixed by ahand. This allows the movement of the distal end portion of thetoothbrush head 5 to be enlarged and further improves the teeth brushingperformance.

(4) In the present embodiment, the brush attachment shaft tube 11 isbiased toward the rear surface 10 a of the main body case 2, and thefront surface of the basal end portion of the holding part 51 holdingthe brush bristles 52 is arranged rearward toward the rear surface 51 a.Further, the holding part 51 of the toothbrush head 5 is narrowed fromthe basal end toward the distal end portion. In addition, the frontsurface of the holding part 51 is formed closer to the rear surface 51a. As a result, since the front surface of the holding part 51 does notextend outward, when brushing teeth, the teeth do not hit such anoutwardly extending portion that would make brushing difficult.

(5) In the present embodiment, the main body case 2 is formed by theouter case 10, which includes the brush attachment shaft tube 11, andthe inner case 20, which includes the motor accommodation portion 27that accommodates the motor M at one end and the battery accommodationportion 22 that accommodates the battery B at the other end.Accordingly, just by accommodating the inner case 20 in the outer case10, the motor accommodation portion 27 can be press-fitted into thebrush attachment shaft tube 11 of the outer case 10, and the coupling ofthe motor M to the brush attachment shaft tube 11 is facilitated.

(6) In the present embodiment, the elastic ring R2 is arranged betweenthe main body case 2, or the trunk 21 of the inner case 20, and the gripcase 4. When the inner case 20 (trunk 21) is arranged in the grip case4, the elastic ring R2 is elastically deformed by the inner surface ofthe distal opening of the grip case 4 so that the space between theinner case 20 and the grip case 4 is watertight and elasticallysupported.

Accordingly, the elastic ring R2 suppresses the transmission of theoscillation of the motor M, which is accommodated in the motoraccommodation portion 27 of the inner case 20, to the grip case 4, andthe oscillation is transmitted in a concentrated manner at the side ofthe toothbrush head 5. As a result, the brushing performance is furtherimproved, the oscillation transmitted to the hand holding the grip case4 is decreased, and the teeth are brushed with comfort.

Moreover, the elastic ring R2 has a sealing performance. Thus, whenwashed with water, water can be prevented from entering the main bodycase 2 through between the grip case 4 and the inner case 20.

(7) In the present embodiment, the seal ring R1 is arranged between theouter case 10 of the main body case 2 and the trunk 21 of the inner case20. When washing the electric toothbrush 1 with water, water can beprevented from entering the main body case 2 through between the outercase 10 and the inner case 20.

Moreover, the transmission of oscillation of the motor M, which isaccommodated in the motor accommodation portion 27 of the inner case 20,by the seal ring R1 to the outer case 10 is suppressed and transmittedin a concentrated manner at the side of the toothbrush head 5. As aresult, the teeth brushing performance can be further improved, theoscillation transmitted to the hand holding the outer case 10 isdecreased, and the teeth are brushed with comfort.

(8) In the present embodiment, the toothbrush head 5 attached to themain body case 2 is accommodated in the cap 6 when not in use. Whencarrying the electric toothbrush 1, the toothbrush head 5 (brushbristles 52) does not touch the surrounding. This maintains a hygienestate without the toothbrush head 5 becoming unclean or a pouch, pocket,or the like from becoming unclean. Further, the brush bristles 52 can beprotected without being deformed, and a high rubbing performance can bemaintained. Further, the switch member 13 is not erroneously operated bythe surrounding.

Moreover, when attached to the main body case 2, the profile of the cap6 is such that the outer circumferential surface of the electrictoothbrush 1 is flush with the outer circumferential surface of the gripcase 4. As a result, the outer circumferential surface of the electrictoothbrush 1 is smooth. Thus, when accommodated in a pouch or a pocket,the electric toothbrush 1 does not get hooked to the surrounding, andthe cap 6 does not fall off.

The above embodiment may be modified as described below.

In the above embodiment, the main body case 2 is formed by two members,the outer case 10 and the inner case 20. However, the outer case 10 andthe inner case 20 may be formed integrally to obtain the main body case2. This reduces the number of components and allows for the seal ring R1to be omitted.

In the above embodiment, the elastic ring R2 is arranged between thetrunk 21 of the inner case 20 and the grip case 4. Instead of a ring,elastic members may be arranged at predetermined intervals in thecircumferential direction.

In the above embodiment, an O-ring that is elastic and has a sealingperformance with respect to water is used as the elastic ring R2, whichis arranged between the trunk 21 of the inner case 20 and the grip case4. Instead, an elastic member that is just elastic and does not have asealing performance with respect to water may be used.

In the above embodiment, the elastic ring R2 is arranged between thegrip case 4 and the inner case 20 of the main body case 2. As shown inFIG. 8, the basal end portion in the outer case 10 of the main body case2 may be inserted into the grip case 4, and an elastic ring R3corresponding to the elastic ring R2 may be arranged between the gripcase 4 and the outer case 10.

DESCRIPTION OF THE REFERENCE CHARACTERS

1: electric brush, 2: main body case, 5: toothbrush head, 6: cap, 10:outer case, 10 a: rear surface, 11: brush attachment shaft tube, 20:inner case, 22: battery accommodation portion, 27: motor accommodationportion, B: battery, M: motor, R1: seal ring.

1. An electric toothbrush comprising: a toothbrush head; an oscillationgenerator formed by a motor including an eccentric weight; and a mainbody case attached in a removable manner to the toothbrush head andaccommodating the oscillation generator; wherein the toothbrush head isattached to a brush attachment shaft tube at a distal end of the mainbody case, and the oscillation generator is arranged in the brushattachment shaft tube.
 2. The electric toothbrush according to claim 1,wherein the brush attachment shaft tube is arranged biased toward a rearsurface side of the main body case.
 3. The electric toothbrush accordingto claim 1, further comprising a cap fitted onto the main body case toaccommodate the toothbrush head that is attached to the brush attachmentshaft tube.
 4. The electric toothbrush according to claim 1, wherein themain body case includes an outer case, which includes the brushattachment shaft tube, and an inner case, which includes a motoraccommodation portion that accommodates the motor at one end and abattery accommodation portion that accommodates a battery for drivingthe motor at another end, and the inner case is accommodated in theouter case so that the motor accommodation portion is press-fitted intothe brush attachment shaft tube of the outer case.
 5. The electrictoothbrush according to claim 4, further comprising a seal ring arrangedbetween the outer case and the inner case of the main body case.
 6. Theelectric toothbrush according to claim 1, wherein the brush attachmentshaft tube is entirely arranged in the toothbrush head when thetoothbrush head is attached to the main body case.